Voluntary nystagmus in five generations.

Voluntary nystagmus is not a pathological condition. By voluntary effort, rapid synchronous pendular eye movements in the horizontal plane can be performed. Voluntary nystagmus has a frequency of 10 to 25 Hz, amplitude up to 6 degrees, and can be maintained for up to 35 s. Oscillopsia is a concomitant feature. It has been reported in more than 100 individuals since 1855 but only once in three siblings, or in two generations. This paper reports five cases in five generations of one family and autosomal dominant inheritance with high penetrance is suggested.